1894.] 3IICR0SC0PICAL JOURNAL. 231 



the largest Naviculae, such as N. nobilis, N. major, N. 

 firma, N. rhoraboides, Surirella splendida, Nitzschia 

 sigma and Stauroneis gracilis, existed in the living state 

 in connection with thousands of the empty frustules. 



In all my previous years of experience in collecting 

 diatoms from many sources, living as well as recent, or 

 fossil, I had not found anything similar to this association 

 of species. And perhaps, had it not been for this casual 

 find, the solution of the mystery involved in the cause of 

 motion in the diatoms, might have yet escaped what 

 little biological or analytical skill I now possess, and I 

 would have had to continue in the mental attitude of one 

 who strongly suspects the animal character of the motile 

 diatoms, but cannot crystallize his proof into a concrete 

 expression for lack of demonstrable evidence. But this 

 stage has been safely passed and an easy method of veri- 

 fication is accessible to all who use the microscope as an 

 instrument of research, or for biological studies of any 

 kind. 



On the night of July 4, 1894, I determined that the 

 bottle contained living diatoms, and set it aside until the 

 evening of the 5th, but during the day, I found that the 

 inner sides of both bottles of material, (the one from the 

 eel-grass material of the lake, and the other from the 

 swampy ground) were covered with thousands of liv- 

 ing and moving diatoms that had come up out of the 

 sediment at the bottom of the bottles. After having 

 determined this, my uniform rule had been on each suc- 

 cessive night to take the bottle containing the diatoms 

 secured outside of the lake and twirl the bottle very 

 gently to dislodge the living diatoms from the sides, 

 taking care not to disturb the sediment at the bottom. 

 After twirling the bottle, three-fourths of the clear water 

 was poured into a flexible India rubber hemispherical 

 cup about three inches in diameter. The material was 

 then allowed to settle for two or three minutes, and the 



